FIGS. 1, 2 and 3 depict a prior art battery-powered screwdriver 10 having a bit holding cartridge 12. Screwdriver 10 has a casing 14 within which a compartment 16 is formed for containing battery 17 (shown schematically only in FIGS. 2 and 3). Battery 17 powers motor 18 (shown schematically only in FIGS. 1 and 2) when rocker switch 20 is actuated, rotating shaft 22 about its longitudinal axis. Shaft 22 is drivingly coupled to motor 18 by a gearing mechanism (not shown) within forward compartment 24. A hexagonal cross-section tool bit holding chuck 26 is provided in the open forward end of shaft 22 for removably and lockably receiving any one of a number of different (preferably double-ended) screwdriver type tool bits 27 (FIGS. 1 and 3), or an assortment of drill type tool bits 27A (FIG. 2) removably stored on cartridge 12. The external surface of casing 14 defines a handle for grasping screwdriver 10.
The end of casing 14 opposite shaft 22 is extended rearwardly (i.e. to the right, as viewed in FIGS. 2 and 3) to define a bit holder storage compartment 28 rearwardly of battery storage compartment 16. A pair of opposed flanges 30, 32 are formed to extend circumferentially around the inner cylindrical surface of casing 14, rearwardly of battery storage compartment 16. Flanges 30, 32 are spaced apart to define a circumferential groove 34 for fixedly retaining the circular rim of base 36 of support shaft 38. As best seen in FIGS. 2 and 3, base 36 is flared radially inwardly and rearwardly to define an anchor flange portion 40 at the juncture of base 36 and shaft 38.
A cylindrically apertured sleeve 42 is formed on the central rearward face of support collar 44 and extends rearwardly therefrom. Stop shoulder 46 on support collar 44 circumferentially surrounds shaft 38 for slidable, longitudinal movement of sleeve 42 and collar 44 forwardly or rearwardly along shaft 38 between the closed and open positions respectively shown in FIGS. 2 and 3. The circumferential outward rim of collar 44 is flanged to bear against the inner cylindrical surface of compartment 28 thereby stabilizing cartridge 12 and preventing wobbling of sleeve 42 during slidable movement thereof along shaft 38.
An inwardly flexible retainer 47 is fixed on the rearward end 49 of shaft 38. This can be accomplished, as shown in FIG. 2, by providing external threading 48 on rearward end 49 of shaft 38 and screwing an internally threaded portion (not shown) of retainer 47 onto the threaded shaft end. Alternatively, as shown in FIG. 3, a spring-biased type clip 50 can be provided on the forward end of retainer 47 for snap-fit engagement within a mating flanged portion 51 formed within the rearward end of shaft 38.
Retainer 47 is formed with a plurality of flexible, radially spaced segments 52 separated by slots 54. When bit cartridge 12 is in the closed position shown in FIG. 2, segments 52 flex radially outwardly, forcing the outwardly protruding circumferential ridged portions 56 of segments 52 into snap-fit engagement within radially outwardly enlarged circumferential recess 58 provided between the rearward end of sleeve 42 and the central, forward face of end cap 60 to firmly retain cartridge 12 in the closed position. The forward end of retainer 47 protrudes radially outwardly around the rearward end of shaft 38, thereby serving as an end stop to limit rearward travel of sleeve 42 on shaft 38 when stop shoulder 46 contacts the forward end of retainer 47.
A cylindrically apertured collar 62 is formed around the central, forward face of cap 60. The circumferential inward surface of collar 62 is securely circumferentially bonded to the rearward end of sleeve 42. To move bit cartridge 12 into the open position shown in FIG. 3, the user grasps end cap 60 and draws it longitudinally away from screwdriver 10 (i.e. by pulling end cap 60 to the right, as viewed in FIG. 2). The force so exerted compresses segments 52 of retainer 47 radially inwardly within recess 58, such that ridges 56 circumscribe a reduced circumference capable of passage through the cylindrically apertured portion of sleeve 42, as sleeve 42 is slidably drawn along shaft 38 into the fully open position shown in FIG. 3.
A second collar 64 is formed around the central, forward face of cap 60 circumferentially surrounding collar 62. The forwardly protruding portion of collar 64 is received within the rearward circumferential end of casing 14 when bit cartridge 12 is in the closed position, as shown in FIG. 2.
A plurality of flexible bit holding clips 66 are spaced radially and fixed around the central outer circumference of sleeve 42. One bit can be press fitted and thus removably retained between each opposed pair of clips 66 to removably retain the bit. A plurality of different bits can be similarly removably retained by utilizing all of the available pairs of clips 66 on bit cartridge 12. When cartridge 12 is in the open position shown in FIG. 3, it can easily be rotated with respect to shaft 38, thereby allowing the user to easily inspect all of the bits removably stored on cartridge 12 and select a particular bit. The selected bit can be removed by pulling it outwardly away from the clips 66 which retain it. End cap 60 is then pressed toward screwdriver 10 to slidably replace cartridge 12 within bit storage compartment 28 in the closed position shown in FIG. 2.
Persons skilled in the art will understand that bit cartridge 12, retainer 47 and cap 60 are readily adapted to use with manually operated screwdrivers, for example as disclosed in U.S. Pat. No. 5,265,504.
Retainer 47 is typically formed of plastic or other suitable flexible material. It can be difficult to achieve uniform resilience in multiple batches of retainer 47 for high volume production of screwdriver 10. If different specimens of retainer 47 have different resilience then the operating characteristics of different screwdrivers incorporating those different retainers may be affected. For example, the snap-fit engagement of segments 52 within recess 58 may be relatively tight in one screwdriver, and relatively loose in another screwdriver. Extra effort may be required to move cartridge 12 between its open and closed positions in the case of relatively tight snap-fit engagement of segments 52 within recess 58, whereas cartridge 12 may be insufficiently retained in the closed position in the case of relatively loose snap-fit engagement of segments 52 within recess 58.
The resilience of retainer 47 may also vary over time. For example, when bit cartridge 12 is in the open position retainer 47's segments 52 are compressed within the cylindrically apertured portion of sleeve 42. If cartridge 12 is left open more than several hours, then the capability of segments 52 to flex radially outwardly into snap-fit engagement within recess 58 may be degraded, weakening such engagement and preventing retainer 47 from retaining cartridge 12 in its closed position, thus permitting undesirable slippage of cartridge 12 from the closed position toward the open position. Consequently, it is impractical to display screwdriver 10 for sale in transparent packaging with cartridge 12 in its open position. Such display is however desirable, because it lets prospective purchasers see cartridge 12 and any bits stored therein. The resilience of retainer 47 may also vary with temperature.
This disclosure addresses the shortcomings of retainer 47. The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.